Sliding doors have been used for many years to secure or isolate various enclosures, including those for cold storage facilities, manufacturing plants, warehouses, garages, and other industrial rooms. Unique to cold storage applications is the need for both door speed and sealing of the doors when closed. Also, unique to cold storage applications is the need for good insulating properties of the door panels themselves. To accommodate both the desirability of fast opening and closing, as well as good insulating properties, door panels can be constructed, for example, from light-weight foam.
Inherent to doors used in connection with cold-storage applications are problems associated with air pressure differentials across opposite faces of the door. These differentials can be caused by a large temperature differential between the cold storage area and the area outside of the cold storage area. These pressure differentials, and others caused for example, by ambient wind, tend to push the door panels inward or outward and away from the walls surrounding the door. Air pressure differentials can also be created by a rapidly actuated panel. Any of these causes can displace a door panel out of its intended plane of travel. This is especially true for relatively light weight panels. This displacement can result in improper positioning of the door when it reaches its closed position, thereby creating problems with proper sealing of the doorway. This can also result in wear and ultimately damage to the hardware associated with the door, including the overhead track.
Others have proposed devices for helping to keep a sliding door panel in proper alignment as it slides. For example, U.S. Pat. No. 6,330,763 issued to Kern et al discloses a ring tethered to a door panel, the ring being slidable along a rope attached to the wall. This rope and ring system is proposed to retain door panels in a position near a wall when sliding. However, it appears that the system proposed in Kern has several deficiencies including that the rope and ring tether (slide restraint and slide) would not, especially with flexible door panels, provide sufficient control over the entire panel except for a portion, such as the trailing edge of the panel, where the slide is tethered to the panel.
Another problem associated with industrial doors is that based upon productivity goals, doors are often hit by forklift trucks or the like which traverse the door opening while the door panels are still partially or completely in a closed position. Accordingly, systems have been proposed for permitting sliding doors to be displaced from their normal plane of travel to accommodate the impact force of the vehicle. Kern et al discloses making the slide of its system frangible. This would require keeping and inventory of spare parts (e.g. slide rings) and down time for the door and traffic while the slide was replaced by maintenance personnel. Kern also discloses the use of flexible tether or rope. This flexible material adds to the lack of control of the panel. It also appears inherent to such flexible ropes that they would work only for a finite distance of displacement upon impact.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior doors of this type.